A MAJOR betting agency was forced to shut down an online market for the federal election date just hours before Julia Gillard made the shock announcement last week, after a flurry of mysterious bets.

Sportsbet confirmed that it had become suspicious when a high volume of small bets began to flood in on for a September election date last Wednesday morning, for no apparent reason. Only a handful of people were said to be in the loop on Ms Gillard's plan, including several ministers, some staff, the independents and the Greens.

MPs are subjected to rules that prohibit them from making profit or gain from inside knowledge. News of an announcement had begun spreading around political circles earlier in the day.

A spokesman for Sportsbet confirmed that it had shut betting down to protect the integrity of the market, an hour before Ms Gillard made her announcement.

"We shut it down to protect ourselves and protect our punters," the spokesman said.

"It wasn't a significant plunge but we had a high number of bets come in.

"Betting on politics is something we monitor very closely."

It is believed the total value was several thousand dollars.

Sportsbet had already closed the market by the time the election had been posted on Twitter. The agency even confirmed on the day through its Twitter account that it had a run on the September market before Ms Gillard announced the date.

"September backed from $1.67 to $1.50 on sportsbet.com.au to be month of election in the hours before it was called," the tweet revealed.

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